Transmission of pictures by electricity



M. B. LONG March 19; 1929.

TRANSMISSION OF PICTURES BY ELECTRICITY 2 Sheets-Sheet l lm/ehfor: Maurice 5. Lang Filed Dec 18, 1923 March 19, 1929. 3 LONG 1,706,032

TRANSMISSION OF PICTURES BY ELECTRICITY Filed Dec. 18, 1923 2 Sheets-Sheet 2 mn/enfo/i' Maurice 5. Long Patented Mar. 19, 1929.

UNITED STATES PATENT OFFICE.-

MAURICE B. LONG, 01 GLEN RIDGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TRANSMISSION 01 PICTURES BY ELECTRICITY.

Application. filed December 18, 1923. Serial No. 681,847,

This invention relates to the production of images of pictures and other objects elec trically, and more particularly to the synchronization of thescanning and reproducing 5 elements of such a system.

of the picture. In order to reproduce a facsimile of the picture, such current of varying amplitude is used to reproduce corresponding tone values on the elemental areas of a recording blank. In order to properly locate the reproduced tone values so as to reproduce the picture, the scanning and reproducing elements must operate 1n substantially perfect synchronism.

An object of this invention 1s to -accomplish synchronization in a novel, simple and effective manner.

In one embodiment of the invention, two carrier waves of different frequencies are transmitted over an ordinary telephone circuit. One of these Waves is modulated by varying current from a photo-electric cell for transmitting the picture characteristlcs, while the other is used for producing synchronized movement of the scanning and reproducing elements. The first mentioned waves are also used to effect the release ofthe scanning and reproducing elements simultaneously to commence the transmission process. These elements are driven by phonic wheels, each of which is controlled by a tuning fork. At the sending station, the fork causes the transmission of impulses of synchronizing waves, while at the reproducing station the fork is actually driven by detected current so'that it vibrates in synchronism with the fork at the sending station.

The novel features which are considered characteristic of this invention are set forth with particularity in the appended claims. Itwill be obvious that severalof them are not limited in use to the transmission of pietures but are capable of other uses in the electrical signaling art. The invention, both as to its organization and method of operatlon, will be further explained in the followmg description with reference to the accompanying drawing, consisting of the following figures Fig. 1 shows schematically the apparatus at the sending station and its connection to the transmission circuit.

Fig. 2 shows schematically the apparatus located at the reproducing station and likewlse its connection to the transmission circuit.

The complete system is shown by placing Figs. 1 and 2 side by side, with Fig. 2 on the ri ht hand side.

eferring now to the drawing, a sending drum 5 is driven by a phonic wheel 6 by means of a shaft shown diagrammatically by dotted lines. The coupling between the drum 5 and the phonic wheel 6 is through a friction clutch The phonic wheel 6 is itself driven by tunlng fork SF inwell known manner. An electron discharge oscillator SO supplies carrier Waves which are amplified by electron discharge amplifier SSA and transmitted through circuit 8 and low pass filter SSF'to the line L for transmission to the reproduc- 1ng station of Fig. 2. An extra contact 9 on tunin fork SF short circuits circuit 8 periodical y at the frequency of vibration of the tuning fork SF. At the reproducing station of Fig. 2, these synchronizing waves are transmitted through low pass filter RSF, amphfied in the two stage electron discharge amplifier RSA, and detected by the electron discharge detector RSD to drive the repro- I duclng tuning fork RF by means of impulses of current in driving magnet 10.- The detector RSDconsists of two electron discharge devices connected in parallel, An ammeter A is inserted in the output circuit of detector BSD for maintenance purposes. The

receiving fork RF drives phonic wheel 11 in well known'manner, which in turn drives reproducing drum 12 through friction clutch 13 and shaft 14. The shaft 14 isshown diagrammatically by dotted lines.

A photo-electric cell 15 located inside of sending drum 5 is connected to'the input circuit 16.0f a two-page electron discharge am plifier PCA. Light from a lamp 17 is focused y means of lens 18 upon the surface of sending drum 5, which is transparent. The light my also passes throu h an aperture in an opaque shield 45. On t e surfaceof the drum 5, a transparency of the picture to be transmitted is secured and the light passing through this transparency of the picture causes a varying current from the battery 19 to flow through the photo-electric cell and to be impressed upon the input circuit 16 of amplifier PCA. The output circuit of picture amplifier PCA is connected to an electron discharge modulator PM by means of potentiometer' 20. Another electron discharge oscillator PO supplies carrier waves which are amplified in an amplifier MCA and transmitted through high pass filter SPF to the line L.

Waves from the oscillator PO may be impressed upon the amplifier MCA by either one of two paths. One path extends from the output circuit of the oscillator circuit P0 through shielded transformer 21, potentiometer 22, when switch 23 is closed, circuit 24, modulator PM, output circuit 25 which includes the contact 26 of relay 27, and potentiometer 28 to the input circuit of amplifier MCA. The other path extends from transformer 21, contact 29 of relay 27 and potentiometer 28 to amplifier MCA.

The energizing circuit for the upper wind ing of relay 27 includes battery 46, switch 17 and relay 48. If this energizing circuit is opened at switch 47, the lower winding of relay 27 is effective to close contact 26. When the switch 47 is closed, the upper winding of relay 27 is effective to close contact 29. Under'this same condition, armature 49 of relay 48 is attracted and locks sending drum 5 against rotation.

At the reproducing station, picture carrier waves from the oscillator PO are transmitted by high pass filter RPF, amplified by amplifier EPA, and impressed upon reproducing demodulator RPD. Connected in the output circuit of demodulator RPD is a battery 30, the movable wires of light valve 31, and winding 32 of relay 33.

The opening between the movable wires of light valve 31 controls the amount of light from lamp 43 which affects a sensitive film secured to reproducing drum 12. The light from lamp 43 is focused first upon the movable wires of light valve 31 and then upon the surface of the drum by lenses as shown. The light. is further concentrated by passing through an aperture in the opaque s iield 44.

The armature of relay 33 is held in the position shown with contact 34 closed by the current flowing in winding 32 when carrier waves are impressed upon the input circuit of demodulator RPD. When such waves are not being received, the armature of relay 33 is moved into a position closing contact 35 by current in winding 36 from. battery 37.

The closure of switch 38 completes a cir Q cuit for relay 39 through battery 40. Current in relay 39 attracts its armature 4:1 to lock drum 12 and prevent its rotation. Another circuit for relay 39 through battery 40 is closed when contact 34 of relay-33 is closed, even though the switch 38 is opened. It is to be noted that the closure of switch 38 forms a short circuit about the contact 34, The circuit completed by the closure of switch 42 and contact 35 forms a short circuit about the winding 32 of relay 33.

The oscillators SO and P0 are of well known type and are identical except for the different constants of the circuit required to produce carrier waves of different frequen cies. Each one has a three-electrode electron s0 discharge device having an input circuit coupled to the output circuit by transformer 60. The frequency is determined by the tuned circuit consisting of the left hand winding of transformer 60 and condenser 61. Connected in series with the feed back portion of the output circuit is a high resistance 62. The output waves for transmission purposes are transmitted through potentiometer 63. In the case of oscillator PO, it is preferable to have the potentiometer variable in such a manner that theworking circuit cannot be connected across the entire resistance of the potentiometer.

The amplifiers SSA, PCA, MCA, RSA, and 9 EPA each include three-electrode electron discharge devices and are so designed as to properly transmit and amplify the waves impressed thereon.

Similarly, the detector BSD and demodu- 100 lator RPD employ three-electrode electron discharge devices. A relatively large grid polarizing battery 64 is used in each case to accomplish detection and demodulation. In the demodulator RPD, a tuned circuit consist- 1c; ing of an inductance coil 65 and a condenser 66 is provided to prevent current of carrier frequency from being impressed upon the light valve 31. Circuit 65, 66 is tuned to the frequency of carrier waves produced by os- 110 cillator PO.

The filters are designed according to the principles set forth in Campbell Patent'No. 1,227,113, May 22, 1917.

- Method of operation.

The method scribed. v

The drums 5 and 12 are set at the starting position in any suitable manner. The 120 transparency of the picture is placed on drum 5 and a sensitive recording blank is placed on drum 12. Switch 47 is closed, which locks drum 5 through the energization of relay 48 and closes contact 29 of relay 27. Switch 38 1 is closed, which locks drum l2'by the energization of relay 39. Switch 42 is kept open.

of operation will nowbe dej The circuits of the electron' discharge devices are then energized. Synchronizing carrier waves from the oscillator SO are trans- 13o mitted through amplifier SSA, circuit 8, low I tact 34.

Tuning. fork SF is then set in vibration and phonic wheel 6 is started.v This tends to rotate sending drum through friction clutch 7, but drum 5 is locked by-the armature 49 of relay 48,' At contact 9 of fork SF, the train of carrier waves from oscillator SO is'periodically interrupted at. circuit 8, so that trains of wavesare transmitted to the line L. These waves in detector RSD cause impulses of current in driving magnet 10 todrive tuning fork RF in synchronism with tuning fork SF.

friction clutch 13, but is prevented from doing so by the armature 41 of relay 39.

Switch 23 is now closed, switch 12 is closed and switch38,is opened. Picture carrier waves from oscillator P0 are impressed upon the input circuit of modulator PM, tlie-o1it-- put circuit of which is still opened, however, at contact 26. Drum 12 is still held in locked position by the energiz-ation of relay 39 through a circuit including contact 34: of relay Everything is in readiness now to start the transmission of the picture. Phonic deenergizes relay 48, which unlocks sending drum 5.

The upper winding of relay 27 is deenergized so that contact 26 is closed and the output circuit of picture modulator PM is connected to the input .circuit of amplifier MCA. During the time that the armature of relay 27 is moving from contact 29 to contact 26, the picture carrier waves are interrupted. Such interruption allows the armature of relay 33 to move from contact 31 to contact. 35 because-of the dcenergization of winding 32. This unlocks reproducing drum 12 by the deencrgization of relay 39. The closure of contact 35 places a short circuit around winding 32 so that the subsequent receipt of car 'ier current by demodulator RPD upon the closure of contact 26 cannot again energize winding 32 to lock drum 12.

The varying tone values of the transparency of the picture cause varying currents through the photo-electric cell 15 Carrier Phonic wheel 1.1 is started and tends to drive drum 12 through picture or other object electrically,

waves from oscillator P0 are modulated by these varying currents after amplification in amplifier PCA, and transmitted to thedemodulator RPD. Corresponding varying currents in the output circuit of demodulator RPD cause movement'of the wires of light,

valve 31 so that the light impressed upon the reproducing blank is varied in accordance with the light transmitted through the transparency of the picture at the sending drum 5.

At the conclusion of the process, switch-47 is closed to lock transmitting drum 5. The attendant at the reproducing station observing that the movement of the light valve has ceased, can either open switch 42 or close switch 38 or both to lock the reproducing drum 12.

The drums can then be returned to their starting position in preparation for the transmission of another picture.

Various modifications ot' the specific embodiment of the invention, which has been described, can be made without departing from the scope of the invention as defined in I the appended claims.

What is claimed is:

1. The method of producing images electrically which comprises scanning the elemental areas of a picture or object to produce image currents, transmitting said currents as modulations of a carrier wave, producing the image under the control of the modulated waves, and starting the image producing process by interrupting the carrier waves for a period of time just preceding the commencement of said process.

, 2. The method of producing images electrically which comprises scanning the elemental areas of a picture or object to produce image currents, transmitting said currents as modulations of a'carrier wave, producing the image under the control of the modulated wa ves, delaying the image producing process during a period-of time when carrier waves are being transmitted, starting the process of image production by interrupting the carrier waves for a period of time, and continuing the process by again transmitting the carrier waves.

3. In a system for producing images of a picture; or other object electrically, a source of carrier waves, means to vary the amplitude of carrier waves from said source in accordauce with the tone values of elemental areas of said picture or object, means including a said picture or object, and means responsive to the interruption of the carrier waves from lit) jmovable element for producing an image of 4. In a system for producing imagesof a asource of carrier waves, means to vary the amplitude of carrier Waves from said source in accordance with the tone values of elemental areas of said picture or object, means including a movable element for producing an mage of said picture or ob ect, restraining means to prevent movement of said movable element, and means responsive to the interruption of the carrier Wavesfrom said source to control said restraining means.

5. In a system for producing images electrically, a source of carrier Waves, means 1ncluding a movable element for modifying carrier Waves from said source in accordance with the tone values of elemental areas of a picture or other object, restraining means to prevent the movement of said movable element, means including a second movable element for producing an image of said picture or other object, a second restraining means to prevent the movement of said second movable element, means controlled by carrier Waves from said source to control said second restraining means, and starting means to con trol both said first restraining means and carrier waves from said source.

6. In a system for producing images electrically, a source of carrier waves, means including a movable element to modify carrier waves from said source in accordance With the'tone values of elemental areas of a picture or other object an image of which is to be produced, means including a second movable element for producing the image, separate restraining means to prevent the movement of said movable elements, means controlled by carrier Waves from said source to control one of said restraining means, and means for. simultaneously controlling carrier Waves from said source and said other restraining means.

7. In a system for producing images of a picture or other object electrically, image current producing means, image producing means, means to transmit image currents as modulations of carrier waves of one frequency, and means to transmit synchronizingimpulses as modulations of carrier Waves of a different frequency.

8. In a system for producing images of a picture or other object electrically, image current producing means, image producing means, means to transmit image currents as modulations of ,a carrier current of one frequency, means to transmit synchronizing currents as modulations of a carrier current of a ditl'erent frequency, a common transmission circuit, and frequency selective means for separating said currents.

9. In asystem for producing images'of a picture or other object electrically, a source of carrier Waves means including a movable element to modify carrier waves from said source in accordance With the tone values of elemental areas of said picture or object, means including a second movable element for producing the image, means to synchronize the movement of said movable elements,

separate restraining means to prevent the movement of said movable elements, means controlled by carrier Waves from said source to control one of said restraining means, and means for simultaneously controlling carrier Waves from said source and said other restraining means.

10. In a system for producing images of a picture or other object electrically, a first source of carrier waves, means including a movable element to modify carrier waves from said source in accordance with the tone values of elemental areas of said picture or object, means including a second movable element for producing the image, means including a second source of carrier Waves for syn chronizing said movable elements, separate restraining means to prevent the movement of said movable elements, means controlled by carrier Waves from said first source to control one of said restraining means, and means for simultaneously controlling carrier waves from said first source and said other restraining means.

11. In a system for producing images of a picture or other object electrically, a source of current, means for modifying current from said source in accordance with the tone value variations of the elemental areas of the picture or object, a receiving circuit, means to impress current from said source upon said receiving circuit, means including a movable element for producing the image, restraining means to prevent movement of said movable element When unmodified current is being reccived,'means to release said restraining means, and means for maintaining said releasingmeans in its operative position when modified current is being received.

12' In a system for producing images of a picture or other object electrically, a source of transmitting current, means including movable means for modifying said current in accordance with the tone values of, elemental areas of said picture or object, re-

straining means for said movable means, and

switching means operable in one position to enable current to be transmitted independently of said modifying means and in a second position to simultaneously prevent the transmlssion of current independently of said modifying means, to cause the transmission of modified current, and to release said restraining means.

In a system for producing images of a picture or including a-rotatable element for converting the light characteristics of elemental areas of said picture or rents having characteristics corresponding thereto, -1neans to modulate carrier Waves of said image one frequency in accordance with currents, means including a rotatable element I for producing the image from said modulated ivaves, means to modulate carrier Wavesof other object electrically, means object into electrical cur- I picture or other object electrically, means including a rotatable element for converting the light characteristics of elemental areas of said picture or object into electrical currents having characteristics corresponding there to, means to modulate carrier waves of one frequency in accordance with said image currents, means including rotatable element for producing the image from said modulated waves, means to modulate carrierwaves of a different frequency in accordance with the rate of rotation of said first mentioned rotatable element, means energized by said modulated waves of different frequencies to drive said second mentioned rotatable element at the samerate as said first mentioned rotatable element, means to prevent the rotation of both said rotatable elements, and means to disable saidpreventing means substantially. simultaneously so that both rotatable elements commence to rotate simultaneously.

15'. In a'system for producing images of a picture or other object electrically, means including a rotatable element for converting the light characteristics of elemental areas of said'picture or object into electric currents having characteristics corresponding thereto, means to modulate carrier waves of one frequency in accordance with said image currents, means including a rotatable element for producing the image from said'modulated Waves, means to cause synchronous rotation of both said rotatable elements, means to prevent the rotation of said rotatable elements, means todisable simultaneously said rotation preventingmeans of the first mentioned rotatable element and to prevent the transmission of said carrier waves, and means operative upon the interruption of said carrier waves to disable said rotation preventing means of the second mentioned rotatable element. a

16. In a system for the transmlsslon of pictures by electricity, a transmission circuit, an

electron discharge oscillator for producing carrier waves of one frequency, an electron discharge modulator, a sending drum, a transparency of the picture mounted on, said drum, a photo-electric cell within sa d drum, an amplifier for amplifying picture currents flowing through said photo-electric cell and .for impressing the amplified currents upon said modulator, and'acircuit including means to lock said sending drum in stationary position and to connect, under one condition, said oscillator to said transmission circuit independently of said modulator and to unlock said drum and to connect, under another condition, said oscillator to said modulator.

17. In a system for the transmission of pictures by electricity, a circuit over which carrier waves are received, a reproducin drum, a light valve, an electron discharge emodulator, means to lock said reproducing drum in response to receipt of carrier waves, means to unlock said drum due to an interruption in the receipt of carrier waves, and means to prevent a subsequent locking of said reproducing drum when carrier waves are again received.

18. In a system for the transmission of pictures by electricity, a circuit over which carrier waves are received, a reproducing drum, a light valve, an electron dischar e demodulator, a relay circuit for locking t e reproducing drum, a second relay connected in circuit with the light valve and adapted when carrier current is being received to cause the relay locking circuit to lock the drum and adapted to unlock thedrum when current is interrupted, and means to short circuit the energizin winding of said relay so that it will not waves are again received.

e energized when carrier '19. In a system for the transmission of pictures by electricity, a transmission circuit, an electron discharge oscillator for producing carrier waves of one frequency, a sending drum, a transparency of the picture mounted on said drum, a photo-electric cell within said drum, an amplifier for amplif ing picture currents flowing through said photo-electric cell, an electron discharge modulator to modulate said carrier waves in accordance with said amplified picture currents and to impress modulated waves upon said transmission. circuit, a reproducing drum, a light valve, an electron discharge demodulator actuated by modulated current from said transmission circuit, a circuit ineluding means for locking said sending drum in stationary position and for connecting said oscillator to said transmission circuit either independently of or through said modulator and for disconnecting said oscillator from said transmission circuit, means to lock said reproducing drum in response to receipt of carrier waves independently of said modulator, means to unlock said drum .due to an interruption in the receipt of carrier waves,

acteristics of said picture or object, a source of carrier current, means for modulating the carrier current in accordance with the varia-' tions of the current from said first source and for transmitting-such modulated current over said'circuit, and means responsive to the modulated current for varying said second source of current in accordance with the modulations of the carrier current to maintain synchronism between said sending and receiving members.

21.- The method of producing images electrically which comprises normally transmitprocess at the sources of carrier waves, means to modify the carrier waves from one of said sources in accordance with the tone values 01 elemental areas of said picture or object, means including a movable element for producing said images, and means controlled jointly by waves from said two sources of carrier waves to control the movement of said movable element. y

In witness whereof, I hereunto subscribe my name this lth day of December, A. D.

MAURICE B. LONG. 

